Process of treating hydrocarbon oil



March 26, 1940. s. w. DARLING PROCESS OF TREATING HYDROCARBON OIL NNN.

Patented Mar. 26, 1940 PATENT [OFFICE f 2,194,692. raocass or TREATINGHrDnocARBoN oIL l Sturgis W. Darling, Houston, Tex., assignor, by mesmeassignments, to Texaco Development Corporation, New York, N. Y., acorporation of Delaware `ipplication June 15, 1937, Serial No.` 148,269

14 Claims.

This invention relates to the art of producing gasoline-like 4productsor relatively low-boiling hydrocarbons from relatively high-boilinghydrocarbons.

According to this invention a relatively clean oil stock, preferably acondensate oil obtained by fractionation of vapors in a bubble tower, ispassed through the first portion of a cracking zone which preferablyextends through the radiant section of a furnace wherein the oil ismaintained under high-temperature` and high-pressure conditions toeifect part or all of the desired conversionthereof.r 'I'he heated oil,after passing through this portion of the cracking zone, is divided intotwo streams, one stream being passed to a coking zone, such as anenlarged coke still to supply the heat required to decompose heavy oilintroduced into the coking zonev to a solid coke-like mass.V The otherstream is mixed with a heavy oil containing reflux condensate andunvaporized constituents of a relatively heavy oil, such as, a reducedcrude oil charge, and the combined stream is passed through the latterportion of the cracking zone which preferably extends `through theconvection section of the furnace to eifect viscosity-A breaking of theheavy oil `and further cracking of the clean oil. `'I'he stream ofcombined cracked products leaving the cracking zone is passed into aseparating zone orevaporator to separate vapors and unvaporized oil, thelatter being passed to a flash orvaporizing Zone preferably maintainedunder reduced 'pressure to vaporize volatile constituents therefrom. Allorp'artr of the remaining unvaporized oil or tar residue is passed tothe coke still where it is reduced to coke by the heat derived from thestream of oil from the cracking zone in the radiant section of thefurnace, as above mentioned. Fresh charging oil forfthe process, such as.reduced crude oil, preheated in any suitable manner, is contacted withthe hot vapors from the flash zone and evaporator to form the heavyoilabove` mentioned which contains reflux condensate and unvaporizedconstituents of the vcrude oil. The vapors remaining uncondensed afterbeing contacted with fresh oil are` fractionated to separate light motorfuels,such as gasoline, from insufciently cracked products, such asreflux condensate which is subjected to cracking con-v ditions. d, y

Other advantages and features of the invention will be hereinafter givenin the detailed de- I scrption of the invention in connection with the(or 19e-,48) n paratus adapted for practicing? the methods of thisinvention. I

`Referring, now to the drawing, the reference character Iil designates afurnace or heater housing a cracking zone in the form of a coilrl2. 5 dThe cracking zone I2 extends, for example, through the radiant sectionI4 and the hottest part of convection section I6 of the furnace I0.Clean oil, such as reflux condensate obtained in the process as laterdescribed, is passed through line I8 by the pump 20 into the `preheatingcoil 22/ positioned inthe cooler portion `of `the convection section I6of the furnace` I0. The pre- Y heated cleanoil then passes throughline24 and temperature and high-pressure conditions to bring about thedesired conversion. The oil stream leaving the rst part of the crackingzone is subdivided into two streams, one stream being passed through'aline 26 having a pressurereducing valve 2l intothe coke still28 in orderto supplythe heat required therein to crack the tar residue within thecoke still to a coke-like mass. The other stream is passed through line3E! and is mixed with a heavy oil which contains `relatively heavyreflux condensate and. heavyy unvaporizedv liquid constituents of thecharge introduced into the process,as will be 30 later described,passing through line 32 by means of pump 33. The lines 26 and 30 areprovided with valves to permit controlling the amountsof crackedproducts being passed through the lines. The combined stream is passedthrough the` 35 latter portion of thecracking zone I2 which ispositioned in or which extends through the conoil stream leaving theiirstpart` of the cracking zone through line 30 andadmixed therewithfissubjected to further cracking.

The stream of cracked products leaving the 45 latter portion ofthecracking zone I2 is passed through line Shaving a pressure-reducingvalve 3G into the evaporator or separating zone 38 fof the combinedevaporator andfractionating tower Ml. Before passing the stream ofcracked products into the evaporator 38, a quench oil may be introducedinto liney 34 as at 4`2`, if desired. Due to the reduction in pressureon the heated oil, there is a separation into vapors-Which pass upwardlyin the evaporator, and a` cracked resil tower 58.

due which is collected in the bottom of the evaporator 38. The crackedresidue is passed through line 46 having a pressure-reducing valve 48into the lflash zone 48 of the combined fractionator and crude flashtower 50 maintained at a lower pressure than the evaporator 38. Due tothe reduction in pressure, there is a further vaporization of theunvaporized liquid or residue withdrawn from the evaporator 38, and thevapors pass upwardly in the flash zone 49 of the combined fractionatorand crude ash tower 50. The remaining unvaporized cracked residue or taris collected in the bottom of the flash zone 49. All or a portion of thecracked tar residue may be passed through line into the coke still 28where the tar residue is subjected to further cracking by mixture with aportion of the stream of cracked products leavingvthe first portion ofthe cracking zone I2 through line 26, as hereinbefore described. If thecoke drum 28 is maintained atrabout' the same or higher pressure as thetower 5I), a pump 52 is used to force the cracked residue into the drum28.

Preferably, the cracked tar residue from the flashzone 59 is mixed withthe stream of cracked products'in line 25 before such stream isintroduced into the coke still or drum 28 in order to raise"the'temperature of the cracked residue to a cracking temperature priorto entering the coke drum to thereby facilitate vaporization of thelighter constituents and decomposition of the tar residue to cokethereby obtaining an increase in the "yield of light products from thecracked residue However, the cracked tar residue from flash Zone i9 maybe passed directly to the coke still 28, or a part of the cracked tarresidue may be passed directly Yinto the coke still and another `portionmixed with the stream in line 26 before passing to the coke still 28.Two or more coke stills may be provided so that one still can be in use"while another still is being cleaned.

' The vapors from the top of the coke still 28 are passed through line53 into the lower portion of the fractionating section 54 of thecombined fractionator and crude flash tower 50. Fresh charging stock forthe process, such as reduced crude oil; preferably preheated, is passedthrough line 58`by means of pump 68 and is introduced into the lupperportion of the fractionating section 54 of the combined` fractionatorand crude flash The reduced crude oil charge flows downwardly in thefractionating section 54 countercurrent tothe hot vapors rising from theflash zone 49 and the hot vapors passing through line 53 from the cokestill 28, as hereinbefore described. In this way intimate contactbetween vapors and liquid oil takes place resulting in condensation ofheavier constituents of the vapors and vaporization of lighterconstituents contained in the charge oil.` The vapors leaving thecombined fractionator andcrude flash tower 50 arel passed through line62. The heavy reflux condensate yand unvaporized reduced crude oil arecollected as liquid at the bottom of the fractionating section 54 inthetrap-out tray 66 provided with a hood 68. The liquid collected on thetrapout'tray 65 is passed through line 10 and is forced into the upperportion of the fractionating section '16 ofthe combined evaporator andfractionating tower L18 by means of pump 12. In the fractionatingsection i6 the heavy reflux condensate and unvaporized reduced crude oilare intimately contacted'jwith vthe hot cracked vapors rising from theevaporatorlor.separating zone 38, and in this waythere is a partialcondensation of heavy constituents contained in the vapors andadditional vaporization of some of the unvaporized reduced crude oil.The reflux condensate and unvaporized reduced crude oil are collected atthe bottom of the :fractionating section 16 on trap-out tray 18 providedwith a hood 80. This liquid which collects on the trap-out tray 'I8 isthe heavy oil above mentioned which is pumped through line 32 and mixedwith one portion of the sub-divided stream leaving the first portion ofthe cracking zone I2 through line 38, the mixture being passed throughthe latter portion of the cracking zone |2 extending through theconvection section of the furnace.

The vapors leaving the top of the combined evaporator and fractionatingtower 40 are passed through line 84 into the bottom portion of asecondary fractionating zone, such as a bubble tower 86. The vaporsintroduced into the secondary fractionating Zone 86 through line 84 passupwardly therein and are fractionated to condense insufficiently crackedproducts as reflux condensate which collects in the bottom of thesecondary fractionating zone 86 and forms the clean oil which is passedthrough line I8 into the cracking zone or coil I2 extending through theradiant section I4 of the furnace I0. A cooling coil 81 in the upperpart of the secondary fractionating zone 86 and other methods of reuxingmay be used as will be laterv explained. The vapors of the desired endpoint pass' from the secondary fractionating zone 86 through line 88 andthen through a condenser 98, the distillate being collected in areservoir or collecting drum 92 having a gas outlet 94 and a liquidoutlet 96. The distillate which is drawn oi through line 96 is a motorfuel of the nature of gasoline. A part of the gasoline collected in thecollecting drum 92 may be passed through line 98 by pump |88 into theupper portion of the secondary fractionating zone 86 to act as reuxliquid.

The vapors leaving the top of the combined fractionator and crude flashtower 50 through line 62 may be fractionated in tower 85, but they arepreferably separately fractionated and a part thereof used as reflux inthe secondary fractionating zone 86. The vapors are passed through line|04 into about the middle portion of a gas oil-naphtha fractionatingtower |86 to separate naphtha vapors from insuiiiciently crackedproducts as reflux condensate. As the vapors pass upwardly in thefractionating tower |86 they are fractionated to condense insufficientlycracked products and the desired naphtha vapors pass through line |88and condenser IIB wherein they are condensed. The thus obtainedcondensed naphtha and lighter gaseous hydrocarbons are pumped by meansof pump II 2 into the lower portion of the secondary fractionating zone86 where the naphtha is mixed with and retained to some extent by thegas oil or reilux condensate and then passed through the cracking zoneI2, By mixing the naphtha with the recycle condensate and passing themixture through the cracking zone I2 reforming of the naphtha isaccomplished along with cracking of the gas oil. The gas oilcollectingat the bottom of the fractionating tower |06 is forced through line I I6and cooler ||8 by pump |26, and a part thereof may bepassed through line|22 into the upper portion of the secondary fractionating zone 86 to actas reflux liquid, and the rest of the cooled liquid may be passedthrough line |24 into the top of the fractionating tower |06 to act asreflux liquid therein. Valves are provided in lines |84 and |08 topermit by-passing of the fractionating tower i I 06 through line` I2iVwherebythe vapors are condensed in condenser IIO and the condensed oilis passed to the bottom of fractionator 86 by pump II2.

In a typical operation contemplated by thi invention a reduced crude oilstock or similar heavy oil stock preferably preheated to about q 400 to475 F. in any suitable Way is introduced into the fractionating section54 of the combined fractionator andcrude flash tower 59. The pressure inthe combined fractionator and crude flash tower 50 is maintained atabout 25 to 125 pounds per square inch. 'I'he introduced hot reducedcrude oil is contacted in the fractionating section 54 with hot vaporsrising from the flash zone 49 and with hot vapors coming from thecokestill 28 through line 53. In this way some of the vapors in thefractionating section 54 are condensed to form heavy reflux condensate,and the lighter constituents of the reduced crude oil are vaporized. Amixture of unvaporized crude oil stock and heavy reflux condensate iscollected in the trap-out trayy 66 at the bottom of the fractionatingsection 54, and this mixture is Withdrawn at a temperature of 'about650,-700 F., preferably, about 675 F. and forced into the fractionatingsection 'l0 of the combined evaporator and fractionating zone by meansof the pump 72. The combined evaporator and fractionating rone 4I] ismaintained at a pressure of about 100 to 400 pounds per square inch.

The mixture introduced into the fractionating section 'i0 comesincontact with hot vapors rising from the evaporator or separating zone38 of the combined evaporator and fractionating zone 40 to causevaporization of some of the liquid mixture. At the same time some of thevapors rising from the evaporator or separating Zone 3B are condensed.The vapors leaving the combined evaporator and fractionating zone ortower 40 are passed through line 811 into the bottom of the secondaryfractionating zone 86 wherein they are fractionated. The light productshaving the desired end pointV aretaken off through line 88, condensedand collected in drum 92. During fractionation reflux condensatecontaining insufficiently cracked products collects at the bottom of thebubble tower or secondaryfractionating zone 8S, and this condensate isthe clean oil or recycle gas oil stock which is passed through line i8and through the cracking zone I 2.

The condensate from the bottom of the secondary fractionating Zone 86may be preheated by` passing it through a preheater coil 22 extendingthrough the cooler portion of the convection section I6 of the furnaceI0. The preheated oil is then passed through the first portion of thecracking zone E2 extending through the radiant section M of the furnacewhere it is subjected to a cracking temperature of` about 900 to 11.00`

F., preferably about 990 F., and a pressure between `about 200 and 1000pounds per square inch.

The cracked products leaving the rst portion of the cracking zone i2 aresubdivided into Vtwo streams, one stream being passed through line 26 tothe coke still 28, while the .other stream is passed through line 30 andmixed with the heavy oil passing through line 32. The unvaporized crudeoil and reflux condensate collecting at the' zone or coil I2 extendingthrough the convection section I6 of the furnace I0. 'Ihe heavy oil isat a temperature of about 770860 F. preferably about 840 F.

Before passing this heavy oil through the cracke ing zone I2, it ismixed with a portion of the cracked products leaving the iirst part ofthe cracking zone through line 30 as above mentioned, and by thisadmixture and with heat applied exteriorly to the cracking zone I2, theternperature of the heavy oil is raised to a cracking temperature ofabout 800.to y975 F.preferably about 900 F., while under a pressurebetween about 200 and 1000A pounds per square inch to effect a mildcracking of the heavy oil. After the y heavy oil is mixed with thedivided stream passing through line 30 the combined stream is passedthrough the latter portion of the cracking zone I2 extending through theconvection section I 6 of the furnace I0 where further cracking of theclean oiltakes place, and the hydrocarbons are converted intolow-,boiling hydrocarbons within the gasoline-boiling range having anexcellent anti-knock quality. During its passage through the latterportion of the cracking zone I2 the heavy oil in the combined stream issubjected to a mild cracking or viscosity-breaking operation therebyforming lower boiling products most of which are recovered as refluxcondensate to be subjected to cracking.

The cracked residue from the evaporator or separating Zone 38 in thecombined evaporator andfractionating tower 40 at a temperature of about'770 to 860 F., preferably about 840 is passed into the flash zone 49 ofthe combined fractionator and crude iiash tower which is under lesspressure than the combined evaporator and `fractionating tower 40', andsome flash distillation or vaporization is obtained. The not vaporswhich are released in the evaporator or is at a temperature of about 700F. or above. All

or only a portion of the cracked tar residue is passed to the coke'still 28 through line 5I; A part of the cracked tar residue may bewithdrawn from the bottom of the flash `zone i9 andused as fuel oil. tomo f flash Zone 49 passing through line 5I is preferably mixed with astream of cracked products leaving the first portion of the crackingzone `I2 through line 25 before it is introduced into the coke still 28,but the tar residue may be introduced directly into the coke still 28 ora part thereof may be mixed with the stream of cracked products passingthrough line25 and the` rest passed directly into the coke still. Thisstream of cracked products is at a high temperature about 900-l100 F.,preferably about 990 F., and is utilized to raise the tar residue to acoking temperature and to furthercrack the tar residue to obtain anincreased yield of gasoline or other light hydrocarbon products. Thetemperature of the coke still 23 is maintained at about SSW-900 F.,preferably about 880 F. l

The pressure in the coke still 28 preferably is lower Vthan the pressurein the cracking Zone I2, and, thereforepsome flash distillation orvaporization of the cracked products is obtainedyin the coke still. Apart of the tar residue 'from The cracked tar residue from the bot- 1iii? the ash zone 49 may be used as fuel oil, or all cracked productsfrom the first portion of the cracking zone I2 was diverted'to the cokestill 28 through line 26 before the heavy oil was injected into thelatter portion of the cracking zone 2 through line 32 so as to obtain astream of cracked'products having a high temperature for cracking thetar residue.

The vapors from the coke still 28 are passed through line 53 into thelower portion of the fractionating section 54 of the combinedfractionator and crude flash tower E below the point of .introduction ofthe hot reduced crude oil charge which is introduced through line 58into the fractionating section 5d of the combined fractionating andflash tower 50. These vapors from the coke still contain cracked naphthavapors which are combined with the gas oil for reforming as will bepresently described. Some of the vapors are fractionated in thefractionating section 5l! and the vapors passing overhead through lineG2 `are condensed and the condensate is introduced by pump H2 or throughline |22 into the secondary fractionating zone 86 to be added to the gasoil condensate for recycling through cracking Zone i2 and reforming ofthe cracked naphtha.

The vapors from the top of the combined fractionator and crude ashtow-er 5@ may be condensed to recover a hydrocarbon product, or they maybe passed to the gas-oil naphtha fractionating tower. E05. The liquidfrom the bottom of the fractionating tower H35 may be cooled and passedthrough line |22 to the top of the secondary fractionating Zone 66 asgas oil reflux, or a part of the liquid may be passed through line IMand used as reflux liquid for the fractionating tower m6. The vaporscoming from the top of the fractionating tower H155 are, preferably,condensed and passed to the lower portion of the secondary fractionatingzone 86 to be added to the condensate oil therein. The vapors leavingthe top of the fractionating tower l contain naphtha constituents. Thesevapors are condensed by passing through condenser Ii and the condensateis added to the gas oil or condensate oil in the bottom of the secondaryfractionating zone 8% for reforming the naphtha constituents when thecondensate oil is recycled through line i8 and passed through thecracking zone i2.

The vapors from the secondary fractionating zone 86 may be condensed andthe liquid collected and treated in the usual manner to produce gasolineor the like.

l/Vhile the primary and secondary fractionating zones have been shown inthe drawing in separate towers, it is to be clearly understood thatthese zones can be located in a single tower; also the evaporator andflash zone, while shown in the drawing as parts of a combinedfractionator and crude flash tower, and a combined evaporator andfractionating tower, respectively, can be constructed and used asseparate apparatus as will be apparent to one skilled in the art.

While a particular embodiment of the invention has been described it isto be expressly understood that the invention is not restricted thereto,and various modifications and adaptations thereof may be made withoutdeparting from the spirit of the invention. Y

I claim: l

1. In a process for converting higher-boiling hydrocarbons intolower-boiling ones, in which oil is passed through a cracking Zone andthen into a separating zone to separate vapors from the cracked residue,the vapors being passed through primary and secondary fractionatingzones and the cracked residue being passed to a ash zone to producefurther vaporization thereof, the vapors leaving said secondfractionating zone being condensed and collected as a hydrocarbonproduct having the desired boiling range, the steps which comprisepassing condensate oil from the secondary fractionating Zone to thecracking Zone wherein it is maintained under high-temperature andhigh-pressure conditions to produce conversion of the condensate oil,contacting a relatively heavy oil stock with the hot vapors from theflash zone to Vaporize some of the lighter constituents of the heavy oiland to condense some of the vapors to form reflux condensate andcollecting reux condensate and unvaporized constituents of the heavy oiland passing them to the primary fractionating zone where further contactwith hot vapors occurs, collecting reflux condensate and unvaporizedliquid constituents of the heavy oil in the primary fractionating zoneand admixing such reflux condensate and unvaporized heavy oil with thecracked products passing through the latter part of the cracking Zone toraise the temperature of the admixed condensate and unvaporized heavyoil to a cracking temperature, passing such admixture through the latterpart of the cracking zone to effect conversion thereof and then passingsuch mixture to the separating zone to separate hot vapors which arepassed to the primary fractionating zone.

2. A process for converting higher boiling hydrocarbons into lowerboiling hydrocarbons, which comprises contacting reduced crude oil stockwith hot hydrocarbon vapors to vaporize some of the reduced crude oilstock and to condense soine of the hot vapors as heavy refluxcondensate, collecting the heavy reiluX condensate and unvaporized crudeoil and passing them to a primary fractionating zone wherein they flowdownwardly and contact hot vapors therein, passing the vapors from theprimary fractionating Zone to asecondary fractionating Zone wherein theyare fractionated to separate condensate oil from a hydrocarbon productcontaining lower boiling hydrocarbons, collecting the condensate oilfrom the secondary fractionating zone and passing it as a stream throughthe first portion of a cracking Zone in the radiant section of afurnace, collecting reflux condensate and unvaporized crude fraction inthe primary fractionating zone and admiXing such condensate andunvaporized crude fraction with the first-mentioned stream leaving thecracking zone in the radiant section of the furnace to form a combinedstream and passing the combined stream through the latter portion of thecracking Zone in the convection section of the furnace, passing thetreated and cracked products from thecracking zone to a separating zoneto obtain separation of vapors from cracked residue, passing the vaporsto said primary fractionating Zone, passing the cracked residue to aflash zone maintained at a lower pressure to obtain fiash distillationinto vapors and tar residue, passing the tar residue from the flash Zoneto a coking Zone and diverting a portion of the stream of crackedproducts from the cracking zone in the radiant section of the furnace tothe coking zone to obtain further cracking of the tar residue therein,the stream being diverted before the introduction of the reux condensateand liquid from the primary fractionating zone, and passing the vaporsfrom the coking zone into contact with the reduced` crude'v ingfraction, subjecting the condensed heavy conj,

stituents to elevated temperature and superat mospheric pressure toeiect conversion thereof into lower boiling products, dividing theproducts of conversion into at least two portions, admixing theunvaporized heavy oil with one of the divided portions to supply heat tothe heavy oil and to effect cracking of the heavy oil, separating theproducts of conversion from the admixed stream into hot vapors andunvaporized liquid constituents, using the last-mentioned hot vapors asthe I vapors for contacting the .relatively heavy charging oil stock,passing the unvaporized liquid constituents to anenlarged zone whereinthey are subjected to further conversion, passing another of the dividedportions into the enlarged zone to Supply heat to the unvaporized liquidconstituents in the enlargedzone to subject them to further conversion.

4. A process for converting higher-boiling hydrocarbonsintolower-boiling hydrocarbons which comprises passing oil through acracking zone wherein it is maintained under high-tern-` perature andhigh-pressure conditions to effect the desired cracking, passing aportion of the stream of cracked products into a separating Zone toseparate hot vapors from a cracked residue,

passing cracked residue `thus obtained to aV flash zone under a lowerpressure for further separation into hot vapors and a tar residue,withdrawing the tar residue and passing itto a coking zone, contactingrelatively heavy hydrocarbon oil with the hot vvapors from the ash zoneto vaporize part of the heavy oil, collecting the unvaporized portionsAof the heavy oil and contacting them with the hot vapors from theseparating zone to vaporize` the lighter constituents thereof andcondense some of the heavy constituents from the vapors, andi fur thertreating the separated lighter constituents to separate a relativelylight hydrocarbon fraction therefrom, collecting and admixing theunvaporized portions ofthe heavy oil with the portion ofv the stream ofcracked products passing to the sep; arating zone to thereby raise theheavy oil'v to cracking temperature and eect cracking thereof, andpassing another portion of the stream of` hot cracked products from thecracking zone to the coking zone to effect cracking of the tar resi' dueintroduced into the coking zone.

5. A` process for converting higher boiling hy'- drocarbons into lowerboiling hydrocarbons, which comprises contacting relatively heavy oilstock with hot vapors in a fractionating zone to vaporize some of theheavy oil andv condense some of the vapors as heavy reflux condensate,collect-y ing the heavy reiiux condensate and unvaporized of the heavyoil stock and to condense some of i the h'otvapors, passing the vaporsfrom the. pri--4 constituents of the heavy oil stock and passingvtionating zone whereinthey are fractionated to separate condensate oilfrom lighter hydrocarbon vapors which are condensed and the distillateseparated as a desired product, collecting the condensate oil from thesecondary fractionating zone and passing it through a portion of acracking zone whereinl it is maintained under high temperature and highpressure conditions to effect the desired conversion, collecting refiux`condensate and unvaporized constituents of the4 heavy oil in the primaryfractionating zone and passing them through another portion of thecracking zone after the reiiux condensate and unvaporized constituentsof the heavy oil rare commingled with cracked products coming from thefirst mentioned portion of the cracking zone, and passing the commingledtreated and cracked products from the cracking Zone toa separating zoneto separate hot vapors from cracked residue and passing such hot vaporsinto the primary fractionating zone tofsupply hot vapors thereto,directing cracked residue from said separating Zone to a flash zonewherein separation of vapors from tar residue takes place under a lowerpressure and passing resultant separatedvapors to the first-mentionedfractionating zone, passing the vapors from said first mentionedfractionating zone to a fractionating tower to obtain gasoil and naphthafractions, introducing the naphtha fraction into the bottom portion ofthe secondary fractionating Zone 4and introducing the gas-oil fractioninto the top portion of the secondary fractionating zone toeifectcondensation l of heavy constituents of the vapors therein which areaddedto the condensate oil in the secondary fractionating zone.

6. A process as defined in claim 5 wherein tar residue from the flashZone is passed to a `coking zone and at least a portion of the crackedproducts from the first mentioned portion of said cracking zone isdiverted to said coking zone to crack the tar residue.

7. A process for converting higher boiling hydrocarbons into llowerboiling hydrocarbons, which comprises introducing relatively heavy oilstock into the fractionating section of a hash tower `in contact withhot vapors therein to vaporize some of the -heavy oil and condense someof the vapors as heavy reflux condensate, collecting the heavy refluxcondensate and unvaporized constituents of such heavy oil stock andpassing them to a primary fractionating zone in contact with hotvaporstherein to vaporize some of the heavy reflux condensate and unvaporizedconstituents of the heavy oil stock and to condense some ofthe hotvapors, passing the vapors from the primary fractionating zone to asecondary fractionatingk zone kwherein they are fractionatedl toseparate condensate oil from a light hydrocarbon product adapted for useas a motor fuel, collecting the condensate oil from the secondaryfractionating Zone and passing it through a cracking zone wherein it is`maintained under hightemperature `and high pressure conditions to`effect the desired conversion, collecting the reflux condensate andunvaporizedi constituents v of the heavy oil' in the primaryfractionating zone and miiclngthem with cracked products coming fromsaid cracking Zone to raise the temperature of the introduced reuxcondensate and unvaporized constituents of the heavy oil to a crackingtemperature and effect cracking thereof, and passing the commingledtreated and cracked products to` a separating zone to separate hot `maryfractionating zone to a secondary frachot vapors into the primaryfractionating zone to supply hot vapors thereto, directing crackedresidue from said separating zone to the aforesaid flash tower whereinseparation of vapors from tar residue takes place under a lower pressureand the separated vapors pass into the fractionating section thereofinto contact with the introduced heavy oil stock, passing the vaporsfrom said fractionating section to a fractionating tower to obtaingas-oil and naphtha fractions, introducing the naphtha fraction into thebottom portion of the secondary fractionating zone and introducing thegas-oil fraction into the top portion of the secondary fractionatingzone to effect condensation of heavy constituents of the vapors thereinwhich are added to the condensate oil in the secondary fractionatingZone.

8. A process as defined in claim 7 wherein tar residue from the flashtower is passed to a coking Zone and at least a portion of the crackedproducts from` said cracking Zone is diverted to said coking Zone, thecracked products being diverted before admixture therewithl of thereflux condensate and unvaporized constituents of the heavy oil.

9. A process for converting higher boiling hy-` drocarbons into lowerboiling hydrocarbons which comprises passing oil as a stream through aprimary cracking zone wherein it is maintained under high temperatureand high pressure conditions to effect the desired extent of cracking,passing a portion of the stream of resultant cracked products through asecondary cracking zone thence into a separating zone to separate hotvapors from a cracked residue, fractionating the vapors to separatelower boiling hydrocarbons as a product, passing cracked residue thusobtained to a flash zone under a lower pressure for further separationof hot vapors and a tar residue, withdrawing the tar residue and passingit to a coking zone, contacting relatively heavy hydrocarbon oil withcracked vapors from said separating zone to vaporize some of the heavyhydrocarbon oil, admixing unvaporized portions of the heavy yoil withthe portion of cracked products passing tothe secondary cracking zone tothereby raise the unvaporized portions of the heavy oil to crackingtemperature, supplying additional heat to the secondary cracking zone toeffect cracking of the unvaporized portions of the heavy oil, andpassing another portion of the stream of hot cracked products from theprimary cracking zone to the coking zone to eect coking of the tarresidue introduced into said coking zone.

10. A process for converting higher boiling hydrocarbons into lowerboiling hydrocarbonswhich comprises passing oil as a stream through acracking zone wherein it is maintained under high temperature and highpressure conditions to effect the desired cracking, passing a portion ofthe stream of cracked products into a separating zone to separate hotvapors from a cracked residue, passing cracked residue thus obtained toa ash zone under a lower pressure 4for further separation vinto hotvapors and a tar residue, withdrawing the tar residue and passing it toan enlarged Zone, contacting relatively heavy hydrocarbon oil with thehot vapors from the flash zone to vaporize part of the heavy oil,collecting the unvaporized portions of the heavy oil and contacting themwith the hot vapors from the separating zone to vaporize the lighterconstituents thereof and condense some of the heavier constituents oftheV vapors and separating the remaining vapors vapors from crackedresidue and passing suchas a" lower boiling hydrocarbon fraction,collecting and admixing the unvaporized portions ofthe heavy oil withthe portion of the stream of cracked products passing to the separatingzone to thereby raise the heavy oil portions to cracking temperature,supplying additional heat to the admixture to effect cracking of theheavy oil portions, and passing another portion of the stream of hotcracked products from the cracking zone to said enlarged zone to effectcracking of the tar residue introduced into said enlarged Zone.

i1. A process for converting high boiling hydrooarbons into low boilinghydrocarbons which comprises introducing relatively heavy charging stockinto contact with hot vapors in a primary fractionating zone, passingvapors from the primary fractionating zone to a secondary fractionatingzone wherein fractionation takes place to separate a reflux condensatefrom lighter fractions, subjecting reflux condensate from the secondaryfractionating zone to cracking conditions of temperature and pressure toeiect conversion into lower boiling products, dividing the products ofconversion into at least two portions, admixing resultant `refluxcondensate and unvaporized charging stock from the primary iractionatingzone with one of the divided portions to supply heat to the heavy oiland to effect cracking thereof, passing resultant products of conversioninto a separating zone wherein separation or" vapors from residualconstituents takes place, passing resultant separated vapors to saidprimary fractionating zone, subjecting residual constituents derivedfrom said separating zone to further cracking by contacting suchresidual constituents with the other of the divided portions of theaforesaid products of conversion.

12. A process for converting high boiling hydrocarbons into low boilinghydrocarbons which comprises introducing relatively heavy charging stockinto contact with hot vapors in a primary fractionating Zone, passingvapors from the primary fractionating zone to a secondary fractionatingzone wherein fractionation takes place to separate a reflux condensatefrom lighter fractions, subjecting rei-lux condensate from the secondaryfractionating zone to cracking conditions of temperature and pressure toeffect conversion into lower boiling products, dividing the products ofconversion into at least two portions, admixing resultant refluxcondensate and unvaporized charging stock from the primary fractionatingzone with one of the divided portions to supply heat to the heavy oiland to effect cracking thereof, passing resultant products of conversioninto a separating zone wherein separation of vapors from residualconstitutents takes place, passing resultant separated vapors to saidprimary fractionating zone, directing resultant liquid residue to aashing zone wherein the residue is subjected'to ash distillation,passing residue from said flashing zone to a coking zone and subjectingthe residue therein to coking by contacting it with the other portion ofaforesaid products of conversion.

13. A process for converting higher boiling hydrocarbons into lowerboiling hydrocarbons which comprises introducing relatively heavycharging stock into a fractionating Zone receiving vapors from theflashing zone hereinafter specified, withdrawing resultant refluxcondensate and unvaporized charging stock'and directing the oil sowithdrawn to a primary fractionating zone of the separating zonehereinafter specified, passing vapors from said primary fractionat- 75ing Zone to a secondary fractionating zonewherein fractionation takesplace to separate reflux condensate from lighter fractions, passingresultant reflux condensate from said secondary fractionating zonethrough a primary cracking zone subject such mixture to' cracking,passing the i resultant treated and cracked products to a separatingzone wherein vapors separate from cracked residue, passing resultantseparated vapors intosaid primary fractionating zone, directingresultant cracked residue from the separating zone to the aforesaiddashing zone wherein separation of vapors from residue takes place andfrom. which the vapors pass to the aforesaid fractionat-v ing zone ofthe flashing Zone, passing resultant residue from the flash zone to acoking zone and diverting a portion of the high temperature crackedproducts from the cracking zone to the coking zone to effect coking ofthe cracked residue introduced thereto, the cracked products beingdiverted before the introduction into the cracking zone of the refluxcondensate and unvaporized charging stock from the primary fractionatingZone. i

14. A process `for converting high boiling vhydrocarbons `into lowerboiling hydrocarbons which comprises introducing relativelyl heavycharging stock into a fractionating zone receiving vapors from theashing zone hereinafter specified, withdrawing resultant refluxcondensate and unvaporized charging stock and directing the oil sowithdrawn to a primary fractionating zone of the separating zonehereinafter specied, passing uncondensed vapors from said primaryfractionating zone to a secondary fractionating Zone whereinfractionation takes place to separate a reux condensate from lowerboiling fractions, passing resultant reflux condensate from saidsecondary fractionating zone through a portion of a cracking zone in aradiant section of a furnace wherein the condensate oil is maintainedunder cracking conditions of temperature and pressure to effect thedesired conversion into lower boiling oils, withdrawing resultant reuXcondensate and unvaporized charging stock from said primary'fractionating zone and combining such reflux condensate and unvaporizedcharging stock with cracked `products from said radiant section andlpassing the mixture through another portion' of the cracking zone in aconvection section of the furnace, directing the resultant cornmingledand cracked products to a separating Zone wherein vapors separate fromcracked residue, passing resultant separated vapors into said `primaryfractionating zone, directing resultant cracked residue from theseparating zone to the aforesaid hashing rzone wherein separation ofvapors from residue takes place and from which the vapors pass to theaforesaid fractionating i Zone of the ashing Zone, passing vapors fromthe oil fraction into an upper portion of said secondary fractionatingzone to effect condensation of constituents therein which are added tothe reux condensate in the secondary fractionating zone.

' STURGIS W. DARLING.

